The present invention relates to a guiding and braking unit comprising a guide cylinder and a rotating roller resting against the cylinder.
In machines for the processing of different types of material webs the material web in general is guided through the machine between a number of processing stations with the help of different types of guiding elements. When the material web is to change direction, guide rollers are used over which the web moves with a larger or smaller enclosed angle. The guide rollers may be suspended in the frame of the machine so that they can freely rotate or they may be connected to a driving element such as an electric motor. To prevent the material web from wandering sideways when it passes over the guide cylinder, owing to inaccuracies in the web itself or in the elements guiding it, lateral guides may be placed before or after the guide cylinder. It is also customary to provide the guide cylinder with guide flanges which are at a mutual distance corresponding to the width of the material web.
Both these methods make it necessary for the guides or guide flanges to be reset or substituted when a material web of another web width is to be processed in the machine. The arrangements are also sensitive to small, otherwise permissible, variations in the width of the material web. In the case of material webs of the "semi-rigid" type, such as the packing laminates of paper and plastics which are used in the manufacture of packing containers for liquid contents, the guide elements sometimes cause damage through wear and buckling along the edges of the web.
Moreover, it is generally important in packing machines that the material web, while being fed through the machine, should be kept relatively well stretched. This is achieved in general by means of braking devices resting directly or indirectly against the web such as braked guide cylinders.
It is an object of the present invention to provide a combined guiding and braking unit which can replace earlier separate arrangements for guiding and braking without being subject to the same disadvantages.
It is a further object of the present invention to provide a guiding and braking unit which has a simple and reliable design and which is economical in its manufacture and can be used in many types of machines for the processing of webs.
It is a further object of the present invention to provide a guiding and braking unit which, without adjustment, can be used for different web widths and which, moreover, requires minimum maintenance.
These and other objects have been achieved in the invention by a a guiding and braking unit comprising a guide cylinder and a rotating roller resting against the cylinder. The roller is adapted to swivel in a plane parallel with the center axis of the cylinder and rest against the cylinder within an angle of 2.degree.-60.degree. degrees from a radius of the cylinder extending perpendicularly to the said plane.
The design of the invention makes possible a combined guiding and braking unit which, even during prolonged operation, effectively retains a material web in the desired axial position in relation to a guide cylinder. The unit is completely cylindrical and lacks flanges or other elements to guide the web. The unit is self-adjusting and does not require to be reset after alterations of the width of the material web.